Multi-functional detergent-containing additive compositions for gasoline have to satisfy a large number of criteria, amongst the most important of which are:
i) elimination of carburettor and injector fouling; PA1 ii) good detergency in the intake port and intake valve regions of the engine; PA1 iii) elimination of valve stick, a problem often associated with the use of high molecular weight detergents; PA1 iv) corrosion protection; PA1 v) good demulsifying characteristics; and PA1 vi) little or no effect on the Octane Requirement Increase (ORI) of modern engines. PA1 A. polyethers based on propylene oxide and/or butylene oxide with a molar mass of at least 500; and PA1 B. esters of monocarboxylic acids or polycarboxylic acids and alkanols or polyols, whereby these esters have a minimum viscosity of 2 mm.sup.2 /s at 100.degree. C. PA1 A. an alkenyl (including polyalkenyl) succinimide of a polyalkylenepolyamine or polyalkyleneoxypolyamine; PA1 B. the reaction product of an alkenyl (including polyalkenyl) succinic acid or anhydride with a 1-(2-hydroxyethyl)-imidazoline further substituted in the 2-position by an alkyl or alkenyl substituent of 1 to 25 carbon atoms; and PA1 C. a polyalkyleneglycol (MW 480 to 2100) preferably polypropyleneglycol. PA1 i) elimination of carburettor and injector fouling; PA1 ii) good detergency in the intake port and intake valve regions of the engine; PA1 iii) elimination of valve stick, a problem often associated with the use of high molecular weight detergents; corrosion protection; PA1 v) good demulsifying characteristics; and PA1 vi) little or no effect on the Octane Requirement Increase (ORI) of modern engines.
Amongst the most effective ashless detergents for lubricating oils and fuel compositions for internal combustion engines, both spark ignition and compression ignition, are alkyl or alkenyl substituted succinimides of the formula I: ##STR1## where R.sub.1 is an alkyl or alkenyl group, especially a long chain polyalkenyl group, e.g. polyisobutenyl, and D is the residue of a polyalkylenepolyamine, and an immense amount of prior art is available describing the manufacture and use of these compounds as detergents for fuels and lubricating oils. The following prior art is merely a representative selection of the total prior art available in this field and covers what the present applicant believes to be the art closest to the present invention.
First of all, brief reference is made to the following patent specifications, which illustrate various routes available for the preparation of the alkenyl substituted succinimides used in the present invention, and which serve to illustrate various principles involved and which need to be taken into account when considering what is meant by an "alkyl or alkenyl-substituted succinimide detergent". The first and foremost of these is that by the very nature of the methods used in the preparation of these compounds, i.e. the initial alkylation step involving (in most cases, but not all) the reaction of a polyolefin with maleic anhydride, or the subsequent condensation reaction between the resulting alkyl or alkenyl substituted succinic anhydride and a polyamine to produce the succinimide, the products produced in each step will usually be a mixture of compounds, and will usually be used as such, either in the subsequent reaction with the polyamine or as the product detergent, i.e. without any form of purification. In other words, where, as above, reference is made to an alkyl or alkenyl-substituted succinimide detergent of formula I, that detergent will usually (unless specific steps have been taken to produce a pure compound) be a complex mixture of compounds approximating to that formula and including in particular some bis-condensates of the formula II: ##STR2## depending on the mole ratio of anhydride to amine used in the condensation reaction.
That having been said, there are two main routes for the preparation of alkyl or alkenyl-substituted succinimide gasoline detergents: the thermal route and the chlorination route. These are described inter alia in U.S. Pat. Nos. 3,018,250 and 3,361,673, UK Patent 949,981 and EP-A-0355895. An alternative route using a chlorinated polyolefin reactant is disclosed in U.S. Pat. No. 3,172,892.
Turning now to the use of alkyl and alkenyl-substituted succinimides as gasoline detergents, reference is made to the following:
U.S. Pat. No. 3,658,494 (1972), which discloses gasoline and other fuel compositions containing the combination of a dispersant and an oxy compound, that oxy compound being a monoetherglycol or a monoetherpolyglycol, i.e. a glycol or polyglycol end capped at one end by an ether group. The range of dispersants covered by and disclosed in the patent is enormous and is generally stated to by an ester, amide, imidine, amidine or amine salt of a carboxylic acid containing at least 30 carbon atoms, but within that broad range alkenyl succinimides is a preferred sub-group. Likewise a broad range of monoether glycols and polyglycols are disclosed as the carrier oil, including polypropylene glycol monoethers, although without any particular reference to those as a preferred group; indeed the Examples in the patent are based on either ethyleneglycol mono-n-butylether or triethyleneglycol monoethylether as the carrier oil, that is to say, at least as far as the detergent additive combinations for gasoline are concerned. Primarily that patent is concerned with sludge dispersion, evidence being provided that the combination of the dispersant and the oxy compound results in a synergistic effect leading to increased sludge reduction, i.e. decreased sludge formation in the gasoline. Whilst sludge reduction in gasoline will in itself be beneficial in reducing deposits in the fuel supply system of an internal combustion engine and to some extent will help to eliminate deposits in and around the inlet valves and injector systems of the modern internal combustion engine, those deposits are essentially high temperature deposits of a very different character to sludge deposits in the fuel tank itself, and which may get transported through the fuel supply system and give rise to blocked injectors etc., the elimination or reduction of sludge is by no means the whole answer to the problem of eliminating high temperature deposits from in and around the fuel intake systems of the modern engine, and which are of a very different character and origin.
UK Patent 1,269,774 (1972), which discloses an additive combination that improves the water-tolerance of gasoline and other distillate fuels, that combination comprising 1) an oil-soluble ashless detergent, inter alia an alkyl or alkenyl-substituted succinimide, 2) an oil-soluble amine or ammonium salt of a sulphonic acid, and 3) an oil-soluble polyether, preferably a polyoxyalkylene polyol. Esters obtainable by the reaction of a polyoxyalkylene polyol with an acid may be used but appear to be a less preferred alternative. As indicated, the patent is primarily concerned with improving the water-tolerance of gasoline, rather than reducing deposits in and around the fuel inlet ports of internal combustion engines.
UK Patent 1,287,443 (1972), which discloses anti-icing additives for gasolines, and which comprise the combination of (A) a polycarboxylic acid or anhydride or a derivative thereof, and including inter alia imide derivatives, such as, an alkyl or alkenyl-substituted succinimide and (B) a non-aromatic alcohol, glycol or polyol, and preferably a polyethyleneglycol or polypropyleneglycol, that combination again allegedly providing a synergistic anti-icing effect in gasolines, a problem quite remote from the elimination of deposits in and around the inlet valves and injectors of internal combustion engines without giving rise to valve stick or increased ORI.
UK Patent 1,310,847 (1973), which, like the '494 patent referred to above, is concerned with sludge reduction in gasoline, and to that end provides an additive combination comprising (1) at least one oxy compound selected from polyglycols and esters of glycols, polyglycols, monoetherglycols and monoetherpolyglycols with mono-carboxylic acids containing up to 20 carbon atoms, and (2) a fuel-soluble dispersant selected from esters, amides, imides, amidines and amine salts of saturated carboxylic acids containing up to 30 aliphatic carbon atoms, i.e. essentially the same range of dispersants as disclosed in the '494 patent referred to above. Indeed, the whole disclosure is similar, save that the range of carrier oils is slightly different, i.e. glycols and glycol esters, rather than monoether glycols and polyglycols.
U.S. Pat. No. 3,676,089 (1972), which describes a motor fuel composition containing an alkenyl succinimide in combination with a polymer or co-polymer of a C.sub.2 -C.sub.6 unsaturated hydrocarbon. The patent claims that the succinimide by itself has no effect on the prevention of intake valve and port deposits.
UK Patent 1,439,567 (1976), which discloses the use of polyalkylene succinimides in which 1-olefins are polymerised to form the hydrocarbon group of the detergent. The patent claims that these polyalkenyl succinimides are superior detergents to those of the prior art, and unlike the prior art, do not leave viscous sticky deposits over the intake manifold and intake valves.
UK Patent 1,486,144 (1977), which discloses the use of an alkenyl succinimide, a polymeric compound which is a polymer of a C.sub.2 -C.sub.6 unsaturated hydrocarbon and a paraffinic or naphthenic oil having a viscosity SUS at 100.degree. F. of from 350 to 3000.
U.S. Pat. No. 4,240,803 (1980), which discloses the use of an alkenyl succinimide in which the alkenyl group is derived from a mixture of C.sub.16 -C.sub.28 olefins for use in gasoline to reduce engine deposits.
U.S. Pat. No. 4,968,321 (1989 ), which discloses a motor fuel composition which inhibits ORI and intake valve deposit formation and sticking which comprises (1) the reaction product of a hydrocarbyl succinic anhydride and a polyoxyalkylene diamine; (2) a polymeric component which is a polyolefin polymer; (3) a polyalkylene glycol having a molecular weight in the range 500-2000 and (4) a lubricating oil.
EP-A-0374461 (1990), which discloses the use of known detergents containing amino or amido groups to maintain cleanliness of the intake system and, as a carrier oil, a mixture of
EP-A-0349369 (1990), which discloses gasoline detergent compositions comprising as the detergent the condensation product of an alkenylsuccinic acid or anhydride with (1) a 1-(2-hydroxyethyl)imidazoline further substituted in the 2- position by an alkyl or alkenyl group of 1 to 25 carbon atoms, and (2) a polyamine, which may either be a polyalkylenepolyamine or a polyalkyleneoxypolyamine. In addition, the gasoline additive compositions contain, as a carrier oil, a polyalkyleneglycol having a molecular weight in the range 480 to 2100, that carrier oil preferably being polypropylene glycol. In addition those compositions may also contain the usual minor components, e.g. antioxidants, corrosion inhibitors, etc., and the usual aromatic hydrocarbon solvent, e.g. xylene.
EP-A-0353116 (1990), which discloses similar gasoline detergent compositions to those described in EP-A-0349369. Essentially these are (excluding the solvent and the minor, conventional, constituents, i.e. antioxidants, corrosion inhibitors, etc.) three component mixes containing:
A specific example of Component A is a polyisobutenylsuccinimide obtained by reacting polyisobutenylsuccinic acid anhydride (PIBSA) with tetraethylenepentamine. In accordance with the teachings of that disclosure, that polyisobutenylsuccinimide is combined with a corresponding condensate of PIBSA with a substituted imidazoline and a polyglycol, preferably polypropyleneglycol, to form an essentially (solvent and minor ingredients not counting) three-component, multifunctional detergent composition for gasoline and other fuels.
EP-A-0376578 (1990), which discloses three-component deposit control additives for gasolines and which comprise a mixture of a polyalkylenesuccinimide, a low molecular weight liquid polyalkylene which is preferably either a polyethylene, polypropylene or polyisobutylene of up to 500 carbon atoms, and a mineral oil having a viscosity of from 100 to 800 SUS at 100.degree. F. and a minimum viscosity index of 91.
Finally WO 91/13949, which discloses a multi-component fuel additive composition specifically designed to overcome the problem of engine octane requirement increase (ORI) which is associated with many prior art gasoline detergent compositions. In accordance with WO 91/13949 the ORI problem is tackled using an additive formulation which contains, in addition to the detergent, a fuel conditioner component comprising both a polar oxygenated hydrocarbon and an oxygenated compatibilizing agent, preferably an aliphatic alcohol of 6 to 14 carbon atoms. Optional components of the conditioner include a hydrophillic separant, a carrier oil, and an aromatic solvent component.
As will be apparent from the above, there is a substantial body of prior art relating to detergent compositions for gasolines and based on alkyl and alkenyl-substituted succinimides as the detergent component. Some of the later art discussed above seeks to deal with much the same problem as the present invention, namely the formulation of an effective multi-functional detergent composition for internal combustion engines, and especially one which eliminates high temperature deposits around the fuel intake valves and injectors, and elsewhere, without at the same time contributing to valve stick or increased ORI, but in the main seeks to deal with that problem in a different way. For example, solutions such as those proposed in U.S. Pat. No. 4,968,321, EP-A-0349369, EP-A-0353116 and EP-A-0376578 involve additional components (i.e. in addition to the dispersant, the carrier oil or the solvent) leading to possible extra expense. Essentially three component compositions (i.e. detergent/carrier oil/solvent), are disclosed in the earlier items of prior art, especially those patents published in the period 1972-1973, but primarily as sludge dispersant compositions, which as already indicated, is a rather different problem to that now faced by modem internal combustion engine technology. Thus, whilst those patents, such as U.S. Pat. Nos. 3,658,494 and UK 1,310,847, do disclose three component additive compositions very similar to those of the present invention, they do, in fact, have little to teach the person skilled in the art when it comes to elimination of high temperature deposits from the fuel intake and injection systems of internal combustion engines, without at the same time contributing to valve stick and increased ORI, as some of those combinations undoubtedly do. Nor does the person skilled in the art derive much help from patents, such as UK 1,269,744 or 1,287,443, which again relate to a different problem, in those cases water tolerance and anti-icing, respectively.